Name: ribosomes in protein synthesis
Uploaded: 2023-04-30T11:35:37.000Z
Duration: 1 min 27 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

NC K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.1.5

Ribosomes

Eukaryotic ribosomes are protein-synthesizing structures formed inside the nucleolus. The 80S ribosome is divided into large and small subunits.
The large subunit, called the 60S ribosome, consists of 28S, 5.8S, and 5S rRNAs and 49 proteins. The smaller subunit, the 40S ribosome, consists of an 18S rRNA and 33 proteins.
Both subunits are exported out of the nucleus through the nuclear pores. They join for protein synthesis either while floating in the cytoplasm or when attached to the outer nuclear envelope or the rough endoplasmic reticulum.
The mRNA binding site lies within the small ribosomal subunit. The three tRNA binding sites, E, P, and A, are formed at the interface of both ribosomal subunits.
Here, an initiator tRNA is placed at the P or peptidyl site, the new tRNAs are received at the A or aminoacyl site, and the empty tRNAs are released from the E or exit site.
rRNA in the large subunit also catalyzes the peptide bond formation between amino acids.

ribosomes

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that synthesize large quantities of protein&#8212;such as secretory cells in the human pancreas&#8212;can contain millions of ribosomes.
Ribosome Structure and Assembly
Ribosomes are composed of ribosomal RNA (rRNA) and proteins. In eukaryotes, rRNA is transcribed from genes in the nucleolus&#8212;a part of the nucleus that specializes in ribosome production. Within the nucleolus, rRNA is combined with proteins imported from the cytoplasm. The assembly produces two subunits of a ribosome&#8212;the large and the small subunits. These subunits then leave the nucleus through pores in the nuclear envelope. At the start of translation, mRNA binds to a site on the small subunit, and subsequently, a large subunit is also recruited. This step forms a functional ribosome.
Ribosomes may assemble in the cytosol&#8212;called free ribosomes&#8212;or while attached to the outside of the nuclear envelope or endoplasmic reticulum&#8212;called bound ribosomes. Generally, free ribosomes synthesize proteins used in the cytoplasm, while bound ribosomes synthesize proteins that are inserted into membranes, packaged into organelles, or secreted from the cell.
Protein Synthesis
Ribosomes synthesize proteins by bringing together mRNA and transfer RNA (tRNA). Specialized nucleotides of the tRNA, called anticodon loop, bind to the codon of the mRNA. The tRNA carries an amino acid on the other end. In this way, the genetic code from mRNA is translated into a chain of amino acids, one codon at a time. When mRNA binds to the small subunit of the ribosome, tRNA binds to one of three binding sites on the large subunit of the ribosome. The binding sites are called the A (aminoacyl-tRNA), P (peptidyl-tRNA), and E (exit) sites. As the mRNA is translated, new tRNAs are added at the A site; they move to the P site and are released at the E site. Ribosomes catalyze the formation of peptide bonds between adjacent amino acids, resulting in a polypeptide. The growing polypeptide chain threads through an exit tunnel in the large subunit. When the protein synthesis is complete, the ribosomal subunits dissociate.

Ribosomes translate genetic information encoded by messenger RNA (mRNA) into proteins. Both prokaryotic and eukaryotic cells have ribosomes. Cells that ...

Education

JoVE Core

Cell Biology

Unit 1

Translation: RNA to Protein

KEY TERMS AND CONCEPTS

ribosomes in protein synthesis

Ribosomes build proteins by reading messenger RNA, or mRNA, and turning that genetic code into an amino acid chain. Both prokaryotic and eukaryotic cells have ribosomes. Cells that make large amounts of protein, such as secretory cells in the human pancreas, can contain millions of them.

Ribosomes are made of ribosomal RNA, or rRNA, and proteins. In eukaryotes, rRNA is transcribed from genes in the nucleolus, a region of the nucleus that specializes in making ribosomes. There, rRNA joins with proteins that are imported from the cytoplasm. This assembly creates a large subunit and a small subunit, which leave the nucleus through pores in the nuclear envelope.

A functional ribosome forms when mRNA binds to the small subunit and the large subunit is recruited. Ribosomes can form in the cytosol as free ribosomes, or they can attach to the outside of the nuclear envelope or the endoplasmic reticulum as bound ribosomes. Free ribosomes usually make proteins used in the cytoplasm. Bound ribosomes usually make proteins that are inserted into membranes, packed into organelles, or secreted from the cell.

During translation, ribosomes bring mRNA and transfer RNA, or tRNA, together. The anticodon loop of tRNA matches a codon on the mRNA, and the tRNA carries an amino acid on its other end. Ribosomes use this match to read the message one codon at a time and build a polypeptide, which is a chain of amino acids.

The large subunit has three tRNA binding sites called the A site, P site, and E site. New tRNAs enter at the A site, move to the P site, and then exit at the E site. Ribosomes also catalyze peptide bonds between neighboring amino acids, and the growing polypeptide passes through an exit tunnel in the large subunit. When protein synthesis ends, the ribosomal subunits separate.

Ribosomes in Protein Synthesis

translation

How Cells Build Proteins from mRNA

Translation is the cell process that builds proteins from messenger RNA, or mRNA. It comes after transcription and is the final step in gene expression. Ribosomes, which are made of protein and specialized RNA, carry out this process with help from transfer RNA, or tRNA, and other proteins. The result is a chain of amino acids called a polypeptide. Proteins are called the building blocks of life because they make up much of an organism, from muscle fibers and hair to parts of the immune system.

Ribosomes build proteins by reading messenger RNA, or mRNA, and turning that genetic code into an amino acid chain. Both prokaryotic and eukaryotic cells have ribosomes. Cells that make large amounts of protein, such as secretory cells in the human pancreas, can contain millions of them. Ribosomes are made of ribosomal RNA, or rRNA, and proteins. In eukaryotes, rRNA is transcribed from genes in the nucleolus, a region of the nucleus that specializes in making ribosomes. There, rRNA joins with...

trna activation

Charging tRNA for Protein Synthesis

tRNA charging is the step that prepares transfer RNA for protein synthesis. In this process, an amino acid is attached to its matching tRNA by an enzyme called aminoacyl-tRNA synthetase. The charged tRNA can then deliver that amino acid during translation. tRNA charging is a key part of how cells build proteins from genetic information. The transcript focuses on the activation of tRNA and the role of aminoacyl-tRNA synthetases in this process. These enzymes help ensure that the correct amino...

initiation of translation

Translation Begins with Ribosome Assembly

Translation begins when a ribosome assembles on an mRNA molecule and starts reading its code. During this first stage of protein synthesis, the cell prepares the machinery needed to build a protein from amino acids. The small ribosomal subunit binds to the mRNA first. It helps position the message so the ribosome can find the correct start site. Then the initiator tRNA, which carries the first amino acid, pairs with the start codon on the mRNA. After the start codon is matched, the large...

termination of translation

How Protein Synthesis Ends

Protein synthesis ends when translation reaches a stop signal on the mRNA. At this stage, the ribosome no longer adds amino acids to the growing polypeptide chain. Instead, the process shifts to releasing the completed protein.

improving translational accuracy

Boosting Protein Translation Fidelity

Protein translation fidelity helps cells build the right protein from an mRNA message. The ribosome must read each codon correctly and add the matching amino acid in order. Even small errors can change the final protein. The transcript explains how accuracy can be improved during translation. It focuses on the steps that help the ribosome choose the correct tRNA and keep the growing peptide chain on track. These controls reduce mistakes while the protein is being made. This topic is important...

nonsense-mediated mrna decay

Nonsense-Mediated mRNA Decay and UPF Proteins

Nonsense-mediated mRNA decay is a cell quality-control process that removes faulty mRNA before it can make a shortened protein. It helps protect cells from errors during gene expression. The pathway depends on UPF proteins, which help identify and trigger the breakdown of the problem message. This process matters when an mRNA contains a premature stop signal, also called a nonsense codon. Instead of allowing translation to continue, the cell recognizes the defective message and targets it for...

molecular chaperones and protein folding

Chaperones Guide Protein Folding

Molecular chaperones help proteins fold into the correct shape. Protein folding is a key step after a protein is made, because shape affects function. If a protein does not fold properly, it may not work as it should. Chaperones do not become part of the final protein. Instead, they assist the folding process and help proteins avoid harmful misfolding. They are especially important when newly made proteins are still fragile and need support as they take on their proper structure. This topic...

the proteasome

Protein Recycling by the Proteasome

The proteasome breaks down proteins inside cells. It helps control which proteins stay active and which are removed. This process is an important part of protein recycling. Proteins can be tagged for destruction before they enter the proteasome. The cell uses this system to remove proteins that are no longer needed or that must be cleared away. The proteasome then cuts them into smaller pieces. This protein breakdown helps the cell stay organized and function properly. By clearing selected...

regulated protein degradation

How Cells Remove Unneeded Proteins

Cells remove unneeded proteins through regulated protein degradation. This process helps control which proteins stay active and which proteins are broken down. Protein degradation is not random. The cell uses signals to mark proteins for removal at the right time. This regulation lets the cell respond to changing needs and keep protein levels balanced. Regulated protein degradation is an important part of molecular biology. It shows how cells maintain control over their internal processes by...

proteins: from genes to degradation

Protein Synthesis and Breakdown

Proteins are made from genes and later broken down when they are no longer needed. This page follows that path from gene information to protein degradation, or protein breakdown. It shows how cells build proteins and how they remove them at the right time. The process begins with genes, which carry the instructions for making proteins. Those instructions are used to produce proteins with specific jobs in the cell. After a protein has done its work, the cell can degrade it instead of keeping it...

key terms and concepts

See how ribosomes read mRNA, match tRNA, and join amino acids into proteins. Learn the roles of free and bound ribosomes in cells.

Ribosomes in Protein Synthesis | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Louisiana Student Standards for Science

High School

Life Sciences

From Molecules To Organisms: Structures And Processes

HS-LS1-1

Virginia  Standards of Learning

HIgh School

BIO.2

BIO.2.d

Minnesota Academic Standards in Science

Life Science

3.2.1 9L.3.2.1.1

Alabama Course of Study Science

From Molecules to Organisms: Structures and Processes

9-12.B.1.2

9-12.B.1.2.b

Next Generation Science Standards

Florida Department of Education

SC.912.L.16

SC.912.L.16.5

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South Carolina College and Career Ready Science Standards

B-LS1-1.

new-york-state-science-learning-standards

New York State Science Learning Standards

Structure and Function

HS-LS1-1.

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Ribosomes in Protein Synthesis

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